Light emitting diode and manufacturing method thereof

ABSTRACT

A light-emitting diode, comprising: a substrate, the substrate comprising an upper surface, a bottom surface opposite to the upper surface, and a side surface; a first type semiconductor layer on the upper surface, wherein the first type semiconductor layer comprises a first portion and a second portion, and the second portion comprises an edge surrounding the first portion; a light-emitting layer on the first portion; and a second type semiconductor layer on the light-emitting layer, wherein the second portion comprising a first surface and a second surface, and a first distance is between the first surface and the upper surface, and a second distance is between the second surface and the upper surface and is smaller than the first distance; wherein the first surface is rougher than the second surface, and the second surface is located at the edge.

TECHNICAL FIELD

The present application relates to a method of dicing a wafer to improvethe production of light-emitting diodes and decreasing the cost thereof.

DESCRIPTION OF BACKGROUND ART

As the light emitting efficiency of the light-emitting diode (LED) isincreased in recent years, the application of the light-emitting diodehas expanded from decoration lighting to the general lighting. Thelight-emitting diode also has gradually replaced the traditionalfluorescent lamp to be the light source of the next generation.

The final step of producing the light-emitting diodes is dicing thewafer. In the step of dicing, firstly the wafer is cut by laser, andthen the wafer is cleaved into a plurality of light-emitting diodes.Traditionally, the laser ablates or melts the wafer from the wafer'ssurface to the wafer's interior. The wafer has semiconductor stackinglayers on the surface. Thus, when the wafer is ablated or melted by thelaser, the light-absorbing substance which is able to absorb the lightis generated.

The above light-emitting diode can further comprise a sub-mount to forma light-emitting device, wherein the light-emitting device compriseselectric circuitries disposed on the sub-mount, at least a solder on thesub-mount to fix the light-emitting diode on the sub-mount, and anelectrical connection structure to electrically connect an electricalpad of the light-emitting diode (LED) and the electric circuitries ofthe sub-mount. The sub-mount can be a lead frame or a mounting substratefor electrical circuit design and heat dissipation improvement.

SUMMARY OF THE DISCLOSURE

A light-emitting diode, comprising: a substrate, the substratecomprising an upper surface, a bottom surface opposite to the uppersurface, and a side surface; a first type semiconductor layer on theupper surface, wherein the first type semiconductor layer comprises afirst portion and a second portion, and the second portion comprises anedge surrounding the first portion; a light-emitting layer on the firstportion; and a second type semiconductor layer on the light-emittinglayer, wherein the second portion comprising a first surface and asecond surface, and a first distance is between the first surface andthe upper surface, and a second distance is between the second surfaceand the upper surface and is smaller than the first distance; whereinthe first surface is rougher than the second surface, and the secondsurface is located at the edge.

A method of manufacturing a light-emitting diode, comprising the stepsof: provide a substrate; providing a semiconductor stack layer on thesubstrate, wherein the semiconductor stack layer comprises a firstsurface opposite to the substrate; treating the first surface to form asecond surface, wherein the second surface is flatter than the firstsurface; and providing a laser beam through the second surface toseparate the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B schematically show a light-emitting diode in accordancewith an embodiment of the present application;

FIGS. 2A and 2B schematically show a wafer device in accordance with anembodiment of the present application;

FIGS. 3A to 3G schematically show a method of manufacturing thelight-emitting diode in accordance with an embodiment of the presentapplication.

FIG. 4 shows a light bulb having the LED array from any one of the firstto third embodiments.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Exemplary embodiments of the present application will be described indetail with reference to the accompanying drawings hereafter. Thefollowing embodiments are given by way of illustration to help thoseskilled in the art fully understand the spirit of the presentapplication. Hence, it should be noted that the present application isnot limited to the embodiments herein and can be realized by variousforms. Further, the drawings are not precise scale and components may beexaggerated in view of width, height, length, etc. Herein, the similaror identical reference numerals will denote the similar or identicalcomponents throughout the drawings.

First Embodiment

FIGS. 1A and 1B schematically show a light-emitting diode in accordancewith an embodiment of the present application. FIG. 1A shows a top viewof a light-emitting diode comprising a first type semiconductor layer20, a second type semiconductor layer 40 on the first type semiconductorlayer 20, a first electrical pad 23 ohmically contacts the first typesemiconductor layer 20 and a second electrical pad 43 ohmically contactsthe second type semiconductor layer 40. The first type semiconductorlayer 20 comprises a first surface 21 and a second surface 222, whereinthe second surface 222 surrounds the first portion.

FIG. 1B shows the cross-sectional view of the dotted line AA′ in FIG.1A. The light-emitting diode comprises a transparent substrate 10 havingan upper surface 101, a bottom surface 102, and a side surface 103between the upper surface 101 and the bottom surface 102, a first typesemiconductor layer 20 on the upper surface 101, a light-emitting layer30 on the first type semiconductor layer 20, a second type semiconductorlayer 40 on the light-emitting layer 30, a first electrical pad 23ohmically contacts the first type semiconductor layer 20, a secondelectrical pad 43 ohmically contacts the second type semiconductor layer40, and a reflective layer 50 on the bottom surface 102, wherein theside surface 103 comprises a damage region 1031.

The material of the transparent substrate 10 comprises the transparentmaterial, such as sapphire (Al₂O₃), GaN, SiC, AlN, ZnO or MgO, SiO₂,B₂O₃ or BaO, so the transparent substrate 10 can be penetrated by alaser beam which is able to focus on the interior thereof. The damageregion 1031 is formed on the side surface 103 during the laserpenetration and is distant from the upper surface 101 and the bottomsurface 102. The wavelength region of the laser beam comprises 350-500,350-800, 350-1200, 500-1000, 700-1200 or 350-1500 nm. The first typesemiconductor layer 20 comprises a first portion 201 and a secondportion 202, the light-emitting layer 30 is on the first portion 201,and the second type semiconductor layer 40 is on the light-emittinglayer 30. When the first type semiconductor layer 20 is p-typesemiconductor material, the second type semiconductor layer 40 can ben-second type semiconductor. Conversely, when the first typesemiconductor layer 20 is n-type semiconductor material, the second typesemiconductor layer 40 can be semiconductor material. The light-emittinglayer 30 can be intrinsic semiconductor material, p-type semiconductormaterial or n-type semiconductor material. When an electrical currentflows through the first type semiconductor layer 20, the light-emittinglayer 30, and the second type semiconductor layer 40, the light-emittinglayer 30 can emit a light. When the light-emitting layer 30 isAl_(a)Ga_(b)In_(1-a-b)P, the light-emitting layer 30 can emit a red,orange, or yellow light. When the light-emitting layer 30 isAl_(c)Ga_(d)In_(1-c-d)N, the light-emitting layer 30 can emit a blue orgreen light.

The second portion 202 of the first type semiconductor layer 20comprises a first surface 21, a second surface 222 and a third surface221. The second type semiconductor layer 40 comprises a fifth surface 41and a fourth surface 42. The average roughness (Ra) of the first surface21 and that of the fifth surface 41 are larger than 100 nm. The averageroughness (Ra) of each of the second surface 222, third surface 221 andthe fourth surface 42 is in a range of 10 nm to 100 nm, and preferablyis smaller than 50 nm. The second surface 222 and the third surface 221are flatter than the first surface 21, and the fourth surface 42 isflatter than the fifth surface 41. The average roughness (Ra) of thefirst surface 21 and that of the fifth surface 41 larger than 100 nm canreduce the total internal reflection of the light emitted from thelight-emitting layer 30 to increase the light extraction efficiency. Thesecond surface 222, the third surface 221 and the fourth surface 42 areformed by regionally treating the first surface 21 and the fifth surface41 at the same time with the same process, such as wet etching or dryetching, so the difference of the average roughness (Ra) between thefourth surface 42, or the third surface 221, and the second surface 222is smaller than 50 nm. Thus, the depth of the second surface 222 or thethird surface 221 related to the first surface 21 is the same as that ofthe fourth surface 42 related to the fifth surface 41. The depth of thesecond surface 222 or the third surface 221 related to the first surface21 is in a range of 2000 Å and 10000 Å, and preferably in a range of4000 Å and 7000 Å. The depth of the fourth surface 42 related to thefifth surface 41 is in a range of 2000 Å and 10000 Å, and preferably ina range of 4000 Å and 7000 Å.

The first electrical pad 23 is formed on the third surface 221 andohmically contacts the first type semiconductor layer 20. The secondelectrical pad 43 is formed on the fourth surface 42 and ohmicallycontacts the second type semiconductor layer 40. The first electricalpad 23 and the second electrical pad 43 are operable for conducting anelectrical current from outside to flow through the first typesemiconductor layer 20, the light-emitting layer 30, and the second typesemiconductor layer 40. The material of the first electrical pad 23 andthe second electrical pad 43 comprises the metal material, such as Cu,Al, In, Sn, Au, Pt, Zn, Ag, Ti, Ni, Pb, Pd, Ge, Cr, Cd, Co, Mn, Sb, Bi,Ga, Tl, Po, Ir, Re, Rh, Os, W, Li, Na, K, Be, Mg, Ca, Sr, Ba, Zr, Mo orLa, or metal alloy, such as Ag—Ti, Cu—Sn, Cu—Zn, Cu—Cd, Sn—Pb—Sb,Sn—Pb—Zn, Ni—Sn, Ni—Co, Au alloy, or Ge—Au—Ni.

The second surface 222 surrounds the first portion and is thereforelocated at the edge of the light-emitting diode. The width of the secondsurface 222 is in a range of 5 μm and 15 μm, and preferably is 10 μm.Because the average roughness (Ra) of the second surface 222 is in arange of 10 nm to 100 nm, and preferably is smaller than 50 nm, thelaser beam can penetrate the second surface 222 to focus in the interiorof the substrate 10.

The reflective layer 50 on the bottom surface 102 can reflect the lightemitted from the light-emitting layer 30 to increase the lightextraction efficiency. The reflective layer 50 comprises a metal layer,DBR, or the combination thereof. The reflectivity of the reflectivelayer 50 is larger than 70% for the laser beam, of which the wavelengthregion is in a range of 350 nm and 500 nm, 350 nm and 800 nm, 350 nm and1200 nm, 500 nm and 1000 nm, 700 nm and 1200 nm, or 350 nm and 1500 nm.

Second Embodiment

FIGS. 2A and 2B schematically show a wafer device 2 in accordance withan embodiment of the present application. FIG. 2A shows that a waferdevice 2 has a transparent substrate 10 and a plurality of units 1 onthe substrate 10. Any two of the units 1 are spaced by a second surface222. A plurality of light-emitting diodes can be produced by cleavingthe wafer device 2 along the second surface 222.

FIG. 2B shows the cross-sectional view of the dotted line BB′ in FIG.2A. The transparent substrate 10 has an upper surface 101 and a bottomsurface 102. The material of the transparent substrate 10 comprises thetransparent material, such as sapphire (Al₂O₃), GaN, SiC, AlN, ZnO orMgO, SiO₂, B₂O₃ or BaO, so the transparent substrate 10 can bepenetrated by a laser beam which is able to focus on interior thereof.The damage region 1031 is formed in the interior of the substrate 10 andis distant from both of the upper surface 101 and the bottom surface102. The wavelength range of the laser beam comprises 350-500, 350-800,350-1200, 500-1000, 700-1200 or 350-1500 nm.

A first type semiconductor layer 20 is formed on the upper surface 101,which has a plurality of first portions 201 and a plurality of secondportions 202. On each of the plurality of first portions 201, alight-emitting layer 30 is formed thereon, and a second typesemiconductor layer 40 is formed on the light-emitting layer 30. Whenthe first type semiconductor layer 20 is p-type semiconductor material,the second type semiconductor layer 40 can be n-second typesemiconductor. Conversely, when the first type semiconductor layer 20 isn-type semiconductor material, the second type semiconductor layer 40can be p-type semiconductor material. The light-emitting layer 30 can beintrinsic semiconductor material, p-type semiconductor material orn-type semiconductor material. When an electrical current flows throughthe first type semiconductor layer 20, the light-emitting layer 30 andthe second type semiconductor layer 40, the light-emitting layer 30 canemit a light. When the light-emitting layer 30 isAl_(a)Ga_(b)In_(1-a-b)P, the light-emitting layer 30 can emit a red,orange or yellow light. When the light-emitting layer 30 isAl_(c)Ga_(d)In_(1-c-d)N, the light-emitting layer 30 can emit a blue orgreen light.

Each of the plurality of second portions 202 of the first typesemiconductor layer 20 comprises a first surface 21, a second surface222 and a third surface 221. The second type semiconductor layer 40comprises a fifth surface 41 and a fourth surface 42. The averageroughness (Ra) of the first surface 21 and the fifth surface 41 islarger than 100 nm. The average roughness (Ra) of each of the secondsurface 222, the third surface 221 and that of the fourth surface 42 isin a range of 10 nm to 100 nm, and preferably is smaller than 50 nm. Thesecond surface 222 and the third surface 221 are flatter than the firstsurface 21, and the fourth surface 42 is flatter than the fifth surface41. The average roughness (Ra) of the first surface 21 and that of thefifth surface 41 which are larger than 100 nm can reduce the totalinternal reflection of the light emitted from the light-emitting layer30 to increase the light extraction efficiency. The second surface 222,the third surface 221 and the fourth surface 42 are formed by regionallytreating the first surface 21 and the fifth surface 41 at the same timewith the same process, such as wet etching or dry etching, so thedifference of the average roughness (Ra) between the fourth surface 42,or the third surface 221, and the second surface 222 is smaller than 50nm. Thus, the depth of the second surface 222 or the third surface 221related to the first surface 21 is the same as that of the fourthsurface 42 related to the fifth surface 41. The depth of the secondsurface 222 or the third surface 221 related to the first surface 21 isin a range of 2000 Å and 10000 Å, and preferably in a range of 4000 Åand 7000 Å. And, the depth of the fourth surface 42 related to the fifthsurface 41 is also in a range of 2000 Å and 10000 Å, and preferably in arange of 4000 Å and 7000 Å.

The first electrical pad 23 is formed on the third surface 221 andohmically contacts the first type semiconductor layer 20. The secondelectrical pad 43 is formed on the fourth surface 42 and ohmicallycontacts the second type semiconductor layer 40. The first electricalpad 23 and the second electrical pad 43 are operable for conducting anelectrical current from outside to flow through the first typesemiconductor layer 20, the light-emitting layer 30, and the second typesemiconductor layer 40. The material of the first electrical pad 23 andthe second electrical pad 43 comprises the metal material, such as Cu,Al, In, Sn, Au, Pt, Zn, Ag, Ti, Ni, Pb, Pd, Ge, Cr, Cd, Co, Mn, Sb, Bi,Ga, Tl, Po, Ir, Re, Rh, Os, W, Li, Na, K, Be, Mg, Ca, Sr, Ba, Zr, Mo orLa, or metal alloy, such as Ag—Ti, Cu—Sn, Cu—Zn, Cu—Cd, Sn—Pb—Sb,Sn—Pb—Zn, Ni—Sn, Ni—Co, Au alloy, or Ge-Au-Ni. Because the averageroughness (Ra) of the second surface 222 is in a range of 10 nm to 100nm, and preferably is smaller than 50 nm, the laser beam can penetratethe second surface 222 to focus in the interior of the transparentsubstrate 10 under the first surface 101. For the first surface 21,because the average roughness (Ra) thereof is larger than 100 nm, thelaser beam is scattered by the first surface 21 and fails to focus inthe interior of the transparent substrate 10 under the first surface101. Therefore, a laser beam can penetrate the second surface 222 andfocus in the interior of the transparent substrate 10 to form theplurality of damage regions 1031.

A reflective layer 50 is formed on the bottom surface 102 of thesubstrate 10. The reflective layer 50 can reflect the light emitted fromthe light-emitting layer 30 to increase the light extraction efficiency.The reflective layer 50 comprises a metal layer, DBR, or the combinationthereof. The reflectivity of the reflective layer 50 is larger than 70%for a laser beam, of which the wavelength region is in a range of 350 nmand 500 nm, 350 nm and 800 nm, 350 nm and 1200 nm, 500 nm and 1000 nm,700 nm and 1200 nm or 350 nm and 1500 nm.

Third Embodiment

FIGS. 3A to 3G schematically show a method of manufacturing thelight-emitting diode in accordance with an embodiment of the presentapplication. FIG. 3A shows the first step of providing a substrate 10.The transparent substrate 10 has an upper surface 101 and a bottomsurface 102. The material of the transparent substrate 10 comprises thetransparent material, such as sapphire (Al₂O₃), GaN, SiC, AlN, ZnO orMgO, SiO₂, B₂O₃ or BaO, so the transparent substrate 10 can bepenetrated by a laser beam to focus interior thereof.

FIG. 3B shows the step of forming a first type semiconductor layer 20, alight-emitting layer 30, and a second type semiconductor layer 40sequentially. The second type semiconductor layer 40 comprises a fifthsurface 41, and the average roughness (Ra) of the fifth surface 41 islarger than 100 nm. When the first type semiconductor layer 20 is p-typesemiconductor material, the second type semiconductor layer 40 can ben-second type semiconductor. Conversely, when the first typesemiconductor layer 20 is n-type semiconductor material, the second typesemiconductor layer 40 can be p-type semiconductor material. Thelight-emitting layer 30 can be intrinsic semiconductor material, p-typesemiconductor material or n-type semiconductor material. When anelectrical current flows through the first type semiconductor layer 20,the light-emitting layer 30, and the second type semiconductor layer 40,the light-emitting layer 30 can emit a light. When the light-emittinglayer 30 is Al_(a)Ga_(b)In_(1-a-b)P, the light-emitting layer 30 canemit a red, orange or yellow light. When the light-emitting layer 30 isAl_(c)Ga_(d)In_(1-c-d)N, the light-emitting layer 30 can emit a blue orgreen light.

FIG. 3C shows the step of pattern-etching of the second typesemiconductor layer 40, the light-emitting layer 30, and the first typesemiconductor layer 20 to reveal a first surface 21 on the first typesemiconductor layer 20 by dry etching or wet etching. The averageroughness (Ra) of the first surface 21 is larger than 100 nm.

FIG. 3D shows the step of treating the first surface 21 and the fifthsurface 41 to form a plurality of fourth surfaces 42, a plurality ofsecond surfaces 222 and a plurality of third surfaces 221 by dry etchingor wet etching. The step of treating the first surface 21 and the fifthsurface 41 comprises forming a patterned photoresist on the firstsurface 21 and the fifth surface 41, etching the first surface 21 andthe fifth surface 41 where is uncovered by the patterned photoresist,and removing the patterned photoresist. Etching the first surface 21 andthe fifth surface 41 comprises dry etching or wet etching. The depth ofeach of the plurality of second surfaces 222, or the plurality of thirdsurfaces 221, related to the first surface 21 is in a range of 2000 Åand 10000 Å, and preferably is in a range of 4000 Å and 7000 Å. And, thedepth of each of the plurality of fourth surfaces 42 related to thefifth surface 41 is also in a range of 2000 Å and 10000 Å, andpreferably is in a range of 4000 Å and 7000 Å. The average roughness(Ra) of each of the plurality of the second surfaces 222, the pluralityof the third surfaces 221 and the plurality of the fourth surfaces 42 isin a range of 10 nm to 100 nm, and preferably is smaller than 50 nm. Thesecond surface 222 is used for defining a plurality of units 1.

FIG. 3E shows the step of forming a second electrical pad 43 on each ofthe plurality of fourth surfaces 42 and a first electrical pad 23 oneach of the third surfaces 221, and then forming a reflective layer 50on the bottom surface 102. The reflective layer 50 comprises a metallayer, DBR, or the combination thereof and has a reflectivity largerthan 70%. The thickness of the reflective layer 50 is smaller than 5 μm,and preferably is in a range of 2 μm to 3 μm. Before forming thereflective layer 50 on the bottom surface 102, the transparent substrate10 is thinned to a range of 90 μm to 150 μm by polish, such as CMP. Theplurality of first electrical pad 23 and the second electrical pad 43are operable for conducting an electrical current from outside to flowthrough the first type semiconductor layer 20, the light-emitting layer30, and the second type semiconductor layer 40. The material of thefirst electrical pad 23 and the second electrical pad 43 comprises themetal material, such as Cu, Al, In, Sn, Au, Pt, Zn, Ag, Ti, Ni, Pb, Pd,Ge, Cr, Cd, Co, Mn, Sb, Bi, Ga, Tl, Po, Ir, Re, Rh, Os, W, Li, Na, K,Be, Mg, Ca, Sr, Ba, Zr, Mo or La, or metal alloy, such as Ag—Ti, Cu—Sn,Cu—Zn, Cu—Cd, Sn—Pb—Sb, Sn—Pb—Zn, Ni—Sn, Ni—Co, Au alloy, or Ge—Au—Ni.

FIG. 3F shows the step of forming a plurality of damage regions 1031 inthe transparent substrate 10 under the second surface 222 by providing alaser beam 8. The wavelength range of the laser beam 8 comprises350-500, 350-800, 350-1200, 500-1000, 700-1200 or 350-1500 nm. Becausethe average roughness (Ra) of the second surface 222 is in a range of 10nm to 100 nm, and preferably is smaller than 50 nm, the laser beam 8 canpenetrate the second surface 222 and focus in the interior of thetransparent substrate 10 to cut the transparent substrate 10 withoutdamaging the first type semiconductor layer 20. For the first surface21, because the average roughness (Ra) thereof is larger than 100 nm,the laser beam 8 is scattered by the first surface 21 and fail to focusin the interior of the transparent substrate 10 under the first surface101.

FIG. 3G shows the step of providing a cutter 9 for cleaving the firsttype semiconductor layer 20, the transparent substrate 10 and thereflective layer 50 along the second surface 222 and through theplurality of damage regions 1031 in the transparent substrate 10 underthe second surface 222. The plurality of units 1 can be separated toform a plurality of light-emitting diodes.

Fourth Embodiment

Referring to FIG. 4, a light bulb in accordance with an embodiment ofthe present application is disclosed. The bulb 600 includes a cover 602,a lens 604, a lighting module 610, a lamp holder 612, a heat sink 614, aconnecting part 616, and an electrical connector 618. The lightingmodule 610 includes a carrier 606 and a plurality of light-emittingelements 608 of any one of the above mentioned embodiments on thecarrier 606.

The foregoing description of preferred and other embodiments in thepresent disclosure is not intended to limit or restrict the scope orapplicability of the inventive concepts conceived by the Applicant. Inexchange for disclosing the inventive concepts contained herein, theApplicant desires all patent rights afforded by the appended claims.Therefore, it is intended that the appended claims include allmodifications and alterations to the full extent that they come withinthe scope of the following claims or the equivalents thereof.

What is claimed is:
 1. A light-emitting diode, comprising: a substrate,the substrate comprising an upper surface, a bottom surface opposite tothe upper surface, and a side surface; a first type semiconductor layeron the upper surface, wherein the first type semiconductor layercomprises a first portion and a second portion, and the second portioncomprises an edge surrounding the first portion; a light-emitting layeron the first portion; and a second type semiconductor layer on thelight-emitting layer, wherein the second portion comprising a firstsurface and a second surface, and a first distance is between the firstsurface and the upper surface, and a second distance is between thesecond surface and the upper surface and is smaller than the firstdistance, wherein the first surface is rougher than the second surface,and the second surface is located at the edge.
 2. A light-emitting diodeaccording to claim 1, the substrate comprises a transparent substrate.3. A light-emitting diode according to claim 1, wherein the secondportion further comprises a third surface, wherein a distance betweenthe third surface and the upper surface is equal to the second distance,and the third surface comprises a third average roughness (Ra) in arange of 10 nm to 100 nm.
 4. A light-emitting diode according to claim3, further comprises a first electrical pad on the third surface.
 5. Alight-emitting diode according to claim 1, wherein the width of thesecond surface is between 5 μm and 15 μm.
 6. A light-emitting diodeaccording to claim 1, wherein the first distance is 2000 Å to 10000 Ålarger than the second distance.
 7. A light-emitting diode according toclaim 1, wherein the first surface comprises a first average roughness(Ra) larger than 100 nm, and/or the second surface comprises a secondaverage roughness (Ra) in a range of 10 nm to 100 nm.
 8. Alight-emitting diode according to claim 1, further comprising areflective layer on the bottom surface.
 9. A light-emitting diodeaccording to claim 7, wherein the second type semiconductor layercomprises a fifth surface and a fourth surface, and the fifth surface isrougher than the fourth surface.
 10. A light-emitting diode according toclaim 9, wherein the fourth surface comprises a fourth average roughness(Ra) in a range of 10 nm to 100 nm.
 11. A light-emitting diode accordingto claim 10, wherein the difference between the fourth average roughness(Ra) and the second average roughness (Ra) is smaller than 50 nm.
 12. Alight-emitting diode according to claim 1, further comprising a damagedregion on the side surface and distant from upper surface and bottomsurface.
 13. A light-emitting diode, comprising: a first typesemiconductor layer, wherein the first type semiconductor layercomprises a first portion and a second portion, and the second portioncomprises a first surface and a second surface; a light-emitting layeron the first portion; and a second type semiconductor layer on thelight-emitting layer, wherein the second type semiconductor layercomprises a fifth surface, wherein the first surface and the fifthsurface are rougher than the second surface, and the second surfacesurrounds the first portion.
 14. A method of manufacturing alight-emitting diode, comprising the steps of: provide a substrate;providing a semiconductor stack layer on the substrate, wherein thesemiconductor stack layer comprises a first surface opposite to thesubstrate; treating the first surface to form a second surface, whereinthe second surface is flatter than the first surface; and providing alaser beam through the second surface to separate the substrate.
 15. Amethod of manufacturing a light-emitting diode according to claim 14,wherein a damage region is formed in the substrate under the secondsurface by the laser beam.
 16. A method of manufacturing alight-emitting diode according to claim 14, wherein treating the firstsurface to form the second surface comprises forming a third surface atthe same time.
 17. A method of manufacturing a light-emitting diodeaccording to claim 14, wherein the laser beam is scattered by the firstsurface.
 18. A method of manufacturing a light-emitting diode accordingto claim 14, wherein the second surface is nearer to the substrate thanthe first surface.
 19. A method of manufacturing a light-emitting diodeaccording to claim 16, further comprising forming a first electrical padon the third surface before the step of providing a laser beam throughthe second surface to separate the substrate.
 20. A light-emitting diodeaccording to claim 14, the substrate comprises a transparent substrate.